EP1906710B1 - LED-based optical system and method of compensating for aging thereof - Google Patents

LED-based optical system and method of compensating for aging thereof Download PDF

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Publication number
EP1906710B1
EP1906710B1 EP07108327.3A EP07108327A EP1906710B1 EP 1906710 B1 EP1906710 B1 EP 1906710B1 EP 07108327 A EP07108327 A EP 07108327A EP 1906710 B1 EP1906710 B1 EP 1906710B1
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Prior art keywords
led
blocks
rates
compensation
color
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EP07108327.3A
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German (de)
English (en)
French (fr)
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EP1906710A2 (en
EP1906710A3 (en
Inventor
Rustam Abdulaev
Hoon Choi
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Samsung Electronics Co Ltd
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Samsung Electronics Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • G09G3/3426—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines the different display panel areas being distributed in two dimensions, e.g. matrix
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2014—Display of intermediate tones by modulation of the duration of a single pulse during which the logic level remains constant
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/3413—Details of control of colour illumination sources
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
    • G09G3/3406—Control of illumination source
    • G09G3/342—Control of illumination source using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/10—Controlling the intensity of the light
    • H05B45/12—Controlling the intensity of the light using optical feedback
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
    • H05B45/20—Controlling the colour of the light
    • H05B45/22—Controlling the colour of the light using optical feedback
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0233—Improving the luminance or brightness uniformity across the screen
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/02—Improving the quality of display appearance
    • G09G2320/0242—Compensation of deficiencies in the appearance of colours
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/04—Maintaining the quality of display appearance
    • G09G2320/043—Preventing or counteracting the effects of ageing
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0626—Adjustment of display parameters for control of overall brightness
    • G09G2320/064—Adjustment of display parameters for control of overall brightness by time modulation of the brightness of the illumination source
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0666—Adjustment of display parameters for control of colour parameters, e.g. colour temperature
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2320/00—Control of display operating conditions
    • G09G2320/06—Adjustment of display parameters
    • G09G2320/0693—Calibration of display systems
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G2360/00—Aspects of the architecture of display systems
    • G09G2360/14—Detecting light within display terminals, e.g. using a single or a plurality of photosensors
    • G09G2360/145—Detecting light within display terminals, e.g. using a single or a plurality of photosensors the light originating from the display screen

Definitions

  • Apparatuses and methods consistent with the present invention relate to a light emitting diode (LED)-based optical system and a method of compensating for aging thereof. More particularly, the present invention relates to an LED-based optical system and a method of compensating for aging thereof, which may ensure a uniform picture quality by compensating for the non-uniformity of outputs of LED blocks occurring due to the differences in aging speed among the respective LED blocks.
  • LED light emitting diode
  • LEDs have been used for the purpose of illumination, and the development of LEDs for use as a backlight is in full swing.
  • LEDs generate light of a relatively narrow spectrum that is influenced by a band gap of the semiconductor material used.
  • R (red), G (green), and B (blue) LEDs a mixed light and a white light may be generated.
  • a shade difference induced by varying the mixing rates of respective color LEDs appears as a color variation to produce the mixed colors. Accordingly, in the case of producing a lighting fixture using LEDs, the mixing rates among the respective color LEDs should be kept constant.
  • the optical characteristics of an LED may permanently change according to its own characteristics and the surrounding environment, and this permanent change in optical characteristics is called aging or degeneration.
  • the aging speed differs according to the characteristics of the respective LED, and is heightened when the temperature surrounding the LED becomes high or when a high power is supplied.
  • LEDs installed in a large-area display panel are grouped into LED blocks, and in one LED block, LEDs having similar output characteristics are arranged.
  • the output characteristics refer to the amounts of energy outputted from LEDs when the same amount of current is supplied thereto.
  • the colors outputted from the respective LED blocks may differ although they are controlled to output the same color. Due to the color deviation among the LED blocks, partial color non-uniformity may occur in the whole display panel to decrease the picture quality and lead to a user's dissatisfaction.
  • US2006/066265 describes a direct-firing backlight for a display with LEDs provided in independent controllable light emitting regions. Light emitted from each region is compared to a reference value to set a desired colour tone such as CIE tristimulus values.
  • a desired colour tone such as CIE tristimulus values.
  • US2006/0049781 mentions use of a plurality of light sensors to regulate a back-firing backlight.
  • US2005/0058450 mentions a light-emission control circuit.
  • One example aim is to provide an LED-based optical system and a method of compensating for aging thereof, which can remove the non-uniformity of colors among respective LED blocks occurring due to the differences in aging speed among the respective LED blocks.
  • Figure 1 is a block diagram illustrating the construction of a backlight adopting an LED-based optical system according to an exemplary embodiment of the present invention.
  • a backlight comprises a plurality of LED blocks 10-1 to 10-N, an LED driver 20, an red, green and blue (RGB) sensor 50, a control block 30, and a storage unit 40.
  • RGB red, green and blue
  • the backlight is composed of the plurality of LED blocks 10-1 to 10-N, and each LED block includes a plurality R, G, and B LEDs.
  • the R LEDs are connected in series to constitute an R LED group 11
  • the G LEDs are connected in series to constitute a G LED group 12
  • the B LEDs are connected in series to constitute a B LED group 13.
  • the R LED group 11, G LED group 12, and B LED group 13 are connected in parallel, and receive pulse signals from the LED driver 20 connected thereto.
  • the LED driver 20 is connected to one or a plurality of LED blocks 10-1 to 10-N. That is, the LED driver 20 may be connected to all LED blocks 10-1 to 10-N that constitute one backlight, or to a part 10 of the LED blocks.
  • the LED driver 20, under the control of the control block 30, controls pulse widths of pulse signals for determining amounts of current supplied to the R LED group 11, G LED group 12, and B LED group 13 of the LED blocks 10-1 to 10-N. As the pulse width of the pulse signal is widened, i.e., the duty rate of the pulse signal becomes larger, the amount of current supplied to the respective LED groups 11, 12, and 13 is increased.
  • the RGB sensor 50 comprises R, G, and B sensors 51, 52, and 53 for sensing energy outputted from the R, G, and B LED groups 11, 12, and 13, and a sensor board 57 for generating output values of the R, G, and B LED groups 11, 12, and 13 by processing the energy sensed by the respective sensors 51, 52, and 53 as data.
  • the respective sensors 51, 52, and 53 may comprise photodiodes.
  • the sensors 51, 52 and 53 may be installed one by one in the backlight, or alternatively, a plurality of sensor pairs of the R, G, and B sensors 51, 52, and 53 may be installed at predetermined intervals. Additionally, the sensors 51, 52 and 53 may be installed on one side of the backlight.
  • a backlight composed of 6 LED blocks 10 is illustrated.
  • the respective sensors 51, 52, and 53 are installed between a pair of LED blocks 10 arranged on the upper part of the backlight.
  • pairs of groups of sensors 51, 52, and 53 may also be installed in corresponding positions.
  • the sensors 51, 52, and 53 may be configured to have adjustable sensitivities since the sensors 51, 52, and 53 are sensing the outputs of the LED blocks 10 located at difference distances from the sensors. That is, in the case of sensing the output of the LED block 10 arranged adjacent to the sensor group 51, 52, and 53, the sensitivity of the R, G, and B sensors 51, 52, and 53 is adjusted to be decreased, while in the case of sensing the output of the LED block 10 arranged apart from the sensor group 51, 52, and 53, the sensitivity of the R, G, and B sensors 51, 52, and 53 is adjusted to be increased, so that the outputs of the LED blocks 10 can be sensed uniformly.
  • the respective sensor groups 51, 52, and 53 may be provided with different sensitivities, and the sensor groups 51, 52, and 53 for sensing the outputs correspond to the respective LED blocks 10, so that the outputs of the LED blocks 10 can be sensed.
  • a backlight composed of N blocks is illustrated, and the respective sensor groups 51, 52, and 53 are installed at predetermined intervals. Accordingly, the respective sensor groups 51, 52, and 53 sense the outputs of one or more LED blocks 10 arranged adjacent thereto. At this time, since the distances between the respective sensor groups 51, 52, and 53 and the respective LED blocks 10 are almost the same, the respective sensor groups 51, 52, and 53 may be configured to have the same sensitivity.
  • the outputs of the respective LED blocks 10 can be detected by respectively or simultaneously turning on the R, G, and B LED groups 11, 12, and 13 of the LED blocks.
  • the R, G, and B sensors 51, 52, and 53 may sequentially sense the outputs of the R, G, and B LED groups 11, 12, and 13 by sequentially turning on the R, G, and B LED groups 11, 12, and 13 for each LED block 10. Also, by simultaneously turning on the R, G, and B LED groups 11, 12, and 13 included in one LED block 10, the R, G, and B sensors 51, 52, and 53 may simultaneously sense the outputs of the R, G, and B LED groups 11, 12, and 13. In the latter case, the time required for the respective sensors 51, 52, and 53 to sense the outputs may be reduced.
  • the control block 30 generates specified compensation rates by comparing initial output values ( R' x , G' x , B' x ) sensed from the RGB sensor 50 in an initial state with comparison output values ( R x ,G x ,B x ) at a comparison time point, and compensates the output by adjusting the amounts of current supplied to the respective color LED groups 11, 12, and 13 included in the LED blocks 10-1 to 10-N.
  • control block 30 comprises an output sense control unit 31, an output variation rate calculation unit 32, an average calculation unit 33, a compensation judgment unit 34, a compensation rate calculation unit 35, and a pulse width calculation unit 36.
  • the output sense control unit 31 controls the output sensing operation of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N, and stores the output values of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N sensed by the RGB sensor 50 in the storage unit 40.
  • the initial output values ( R' x ,G' x ,B' x ) and the comparison output values ( R x ,G x ,B x ) are stored in the storage unit 40.
  • the initial output values ( R' x ,G' x ,B' x ) are values sensed from the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N in the initial state such as when a backlight product is tested or when the power is initially applied
  • the comparison output values ( R x , G x , B x ) are values sensed from the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N at a certain comparison time point.
  • the storage unit 40 may be a memory device such as an electronically erasable programmable read-only memory (EEPROM) or a flash memory, and comprises an initial value storage part 41 for storing the initial output values ( R' x ,G' x ,B' x ) and a comparison value storage part 42 for storing the comparison output values ( R x , G x , B x ).
  • EEPROM electronically erasable programmable read-only memory
  • flash memory comprises an initial value storage part 41 for storing the initial output values ( R' x ,G' x ,B' x ) and a comparison value storage part 42 for storing the comparison output values ( R x , G x , B x ).
  • the initial value storage part 41 and the comparison value storage part 42 have different addresses.
  • the output sense control unit 31 stores the initial output values ( R' x ,G' x ,B' x ) and the comparison output values ( R x , G x , B x in the initial value storage part 41 and the comparison value storage part 42, respectively, through a process to be described later with reference to Figure 4 .
  • the output variation rate calculation unit 32 calculates the output variation rates R ' x R x , G ' x G x , B ' x B x , which are the rates of the initial output values ( R' x ,G' x ,B' x ) stored in the storage unit 40 to the comparison output values ( R x , G x , B x ), with respect to the LED blocks 10-1 to 10-N.
  • the output variation rates R ' x R x , G ' x G x , B ' x B x are obtained by dividing the initial output values ( R' x ,G' x ,B' x ) by the comparison output values ( R x ,G x ,B x ).
  • the output variation rate calculation unit 32 calculates the respective output variation rates R ' x R x , G ' x G x , B ' x B x of the R, G, and B LED groups 11, 12, and 13 of different colors included in the LED blocks 10-1 to 10-N.
  • 3*N output variation rates R ' x R x , G ' x G x , B ' x B x are generated with respect to the R, G, and B LED groups 11, 12, and 13 of N LED blocks 10-1 to 10-N.
  • the output variation rate R ' x R x of the R LED group 11 of the first LED block 10-1 is expressed as R 1 '/R 1
  • the output variation rate G ' x G x of the G LED group 12 is expressed as G 1 '/G 1
  • the output variation rate B ' x B x of the B LED group 13 is expressed as B 1 '/B 1 .
  • the output variation rate R ' x R x of the R LED group 11 of the N-th LED block 10-N is expressed as R N '/R N
  • the output variation rate G ' x G x of the G LED group 12 is expressed as G N '/G N
  • the output variation rate B ' x B x of the B LED group 13 is expressed as B N '/B N .
  • the average calculation unit 33 calculates average output variation rates of the respective color LED groups 11, 12, and 13 by averaging the output variation rates R ' x R x , G ' x G x , B ' x B x of the R, G, and B LED groups 11, 12, and 13 included in all the LED blocks 10-1 to 10-N. That is, as shown in Equation (1), the average calculation unit 33 calculates the average output variation rate R mean of the R LED group 11 by adding the output variation rates R ' x R x of the R LED groups 11 included in all the LED blocks 10-1 to 10-N and dividing the added output variation rate by N, that is, the number of LED blocks 10-1 to 10-N.
  • the average calculation unit 33 calculates the average output variation rate G mean of the G LED groups 12 and the average output variation rate B mean of the B LED groups 13. Accordingly, three average output variation rates (R mean , G mean , B mean ) are calculated for the respective colors by the average calculation unit 33.
  • the compensation judgment unit 34 judges whether the compensation for the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N is possible by comparing differences between the respective average output variation rates (R mean , G mean , B mean ) of the R, G, and B LED groups 13 and the output variation rates R ' x R x , G ' x G x , B ' x B x of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N, with compensation range values (FaultRange R , FaultRange G , FaultRange B ) predetermined according to the colors.
  • G mean ⁇ G ' x G x ⁇ FaultRang e G
  • B mean ⁇ B ' x B x ⁇ FaultRang e B
  • x denotes the number of corresponding LED blocks 10-1 to 10-N, and this means that through Equation (2), whether the compensation is possible is judged with respect to all the color LED groups 11, 12, and 13 of all the LED blocks 10-1 to 10-N. That is, whether the compensation is possible is judged with respect to 3*N color LED groups 11, 12, and 13.
  • the compensation judgment unit 34 judges that full compensation is impossible if the differences between the output variation rates R ' x R x , G ' x G x , B ' x B x of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N and the average output variation rates (R mean , G mean , B mean ) of the color LED groups 11, 12, and 13 exceed the compensation range values, while it judges that full compensation is possible if the differences are within the compensation range values. This is because if the differences are larger than the compensation range values, it is considered that LEDs included in the corresponding color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N may have been damaged or a measurement error may have occurred.
  • the compensation range values are determined as the differences between the average output variation rates (R mean , G mean , B mean ), which can be calculated on the assumption that the LEDs are not damaged or the measurement error has not occurred, and the output variation rates R ' x R x , G ' x G x , B ' x B x .
  • the compensation rate calculation unit 35 calculates compensation rates ( r x ,g x ,b x ) with respect to the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N of which full compensation is judged to be possible. For this, as shown in Equation (3), the compensation rate calculation unit 35 extracts the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX among the output variation rates R ' x R x , G ' x G x , B ' x B x of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N, and calculates the compensation rates ( r x , g x , b x ) by dividing the output variation rates R ' x R x , G ' x G x , B ' x B x of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N by the maximum values R ' MAX R MAX , G '
  • the compensation rates are the rates of the relative output variation rates among the LED blocks 10-1 to 10-N, and have values that are smaller than or equal to "1" since they are obtained by dividing the output variation values R ' x R x , G ' x G x , B ' x B x by the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX .
  • the compensation rates ( r x , g x , b x ) become "1"
  • the compensation rates ( r x , g x , b x ) become "1"
  • the compensation rates ( r x , g x , b x ) become smaller than the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX
  • the compensation rates ( r x , g x , b x ) become smaller than "1".
  • a larger amount of current than supplied to other LED blocks 10-1 to 10-N should be supplied to the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N of which the compensation rates ( r x ,g x ,b x ) are "1".
  • the threshold values of the current amount supplied to the respective LEDs are fixed according to the characteristics of the LEDs, it is impossible to unlimitedly increase the amount of current. If the amount of current for the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N, of which the compensation is possible, is generally increased, the life span of the LEDs is shortened with the power consumption increased.
  • the compensation is not performed, and the same amount of current as the previous one should be supplied.
  • the compensation is performed, and the amount of current smaller than the current applied to those having a compensation rate of "1" may be supplied.
  • the pulse width calculation unit 36 calculates the pulse widths of pulse signals provided to the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N having the compensation rates ( r x , g x , b x ).
  • PWM R x PWMR ⁇ r x
  • PWM G x PWMG ⁇ g x
  • PWM B x PWMB ⁇ b x
  • PWMR, PWMG, and PWMB denote the pulse widths of the pulse signals provided to the color LED groups 11, 12, and 13 of the existing LED blocks 10-1 to 10-N
  • PWMR x , PWMG *x , and PWMB x are pulse widths of compensated pulse signals.
  • the pulse width calculation unit calculates the pulse widths of the pulse signals only when the compensation rates ( r x ,g x ,b x ) calculated by the compensation rate calculation unit 35 are smaller than "1", and since the compensation rates ( r x ,g x ,b x ) are smaller than "1", the pulse widths of the pulse signals become smaller than the existing ones.
  • the pulse signals having the same pulse widths as the existing ones are provided, while in the case of the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N of which the output variation rates R ' x R x , G ' x G x , B ' x B x are smaller than the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX and the compensation rates ( r x , g x , b x ) become smaller than "1"
  • the pulse signals having the same pulse widths as the existing ones are provided, while in the case of the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N of which the output variation rates R ' x R x , G ' x G x , B ' x B x are smaller than the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX and the compensation rates ( r
  • the amount of current being supplied to the corresponding color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N is varied according to the degree of aging, and thus, compensation of the non-uniformity among the LED blocks 10-1 to 10-N due to the aging may be performed.
  • the brightness of the backlight since the brightness of the backlight is adjusted on the basis of the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N having the highest degree of aging in the compensation process, the brightness of the backlight may be generally lowered. However, such lowered brightness of the backlight can be adjusted using the brightness adjustment function that is used in the existing monitors and so on.
  • the pulse width calculation unit 36 provides the calculated pulse widths of the pulse signals to the LED driver 20, and the LED driver 20 provides the pulse signals having the calculated pulse widths to the corresponding LED groups 11, 12, and 13 of the LED block.
  • Figure 4 is a flowchart illustrating a process of extracting initial output values ( R' x ,G' x ,B' x ) and comparison output values ( R x , G x , B x ) through an output sense control unit of Figure 3 according to an exemplary embodiment of the present invention.
  • the output sense control unit 31 checks markers of the initial value storage part 41 and the comparison value storage part 42 of the storage unit 40 in operation (S301), and confirms whether the initial output values ( R' x ,G' x ,B' x ) are stored in operation (S302).
  • the output sense control unit 31 arranges addresses of the initial value storage part 41 in a row in operation (S303). The arrangement of the addresses is to store the initial output values ( R' x ,G' x ,B' x ) measured by the RGB sensor 50 in the initial state.
  • the output sense control unit 31 turns off the power being supplied to all LED blocks 10-1 to 10-N to cut off the current in operation (S306), and alternately turns on the powers of the LED blocks 10-1 to 10-N in operation (S307). Then, the output sense control unit 31 measures the initial output values ( R' x ,G' x ,B' x ) for the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 using the RGB sensor 50 in operation (S308).
  • the output sense control unit 31 confirms whether the initial output values ( R' x ,G' x ,B' x ) are measured up to the last LED block 10-N in operation (S309), and if the initial output values ( R' x ,G' x ,B' x ) are measured for all the LED blocks 10-1 to 10-N, it stores the measured initial output values ( R' x ,G' x ,B' x ) of the LED blocks 10-1 to 10-N in the initial value storage part 41 of the storage unit 40 in operation (S310).
  • the output sense control unit 31 arranges the addresses of the comparison value storage part 42 in a row in operation (S304). Then, the output sense control unit 31 judges whether the comparison time point, at which the non-uniformity of outputs among the LED blocks 10-1 to 10-N is to be compensated for, has arrived in operation (S305).
  • the output sense control unit 31 turns off the power of all the LED blocks 10-1 to 10-N in operation (S306), and alternately turns on the respective LED blocks 10-1 to 10-N in operation (S307).
  • the output sense control unit 31 measures the comparison output values ( R x , G x , B x ) of the color LED groups 11, 12, and 13 of the turned-on LED blocks 10-1 to 10-N in operation (S308).
  • the output sense control unit 31 can also measure the comparison output values ( R x , G x , B x ) of the color LED groups 11, 12, and 13 in a state that it simultaneously turns on all the LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N to generate a white light.
  • the comparison output values ( R x , G x , B x ) are measured with respect to all the LED blocks 10-1 to 10-N as determined in operation (S309), the measured comparison output values ( R x , G x , B x ) of the respective LED blocks 10-1 to 10-N are stored in the comparison value storage part 42 of the storage unit 40 in operation (S310).
  • the comparison time point for measuring the comparison output values ( R x , G x , B x ) may be diversely set, such as whenever the backlight is turned on or whenever the turn-on time of the backlight elapses, or may be optionally selected by a user.
  • the above-described operation S305 to S310 are repeated.
  • the output sense control unit 31 senses the initial output values ( R' x ,G' x ,B' x ) of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N using the RGB sensor 50, and stores the sensed initial output values ( R' x ,G' x ,B' x ) in the initial value storage part 41 of the storage unit 40.
  • the output sense control unit 31 senses the comparison output values ( R x , G x , B x ) of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N, and stores the sensed comparison output values ( R x , G x , B x ) in the comparison value storage part 42 of the storage unit 40 in operation (S401).
  • the output variation rate calculation unit 32 reads out the initial output values ( R' x ,G' x ,B' x ) and the comparison output values ( R x , G x , B x ) from the initial value storage part 41 and the comparison value storage part 42 of the storage unit 40 in operation (S402), and calculates the output variation rates R ' x R x , G ' x G x , B ' x B x of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N using the read initial output values ( R' x ,G' x ,B' x ) and the comparison output values ( R x , G x , B x ) in operation (S403).
  • the average calculation unit 33 calculates the average output variation rates (R mean , G mean , B mean ) of the color LED groups 11, 12, and 13 by using Equation (1) in operation (S404).
  • the compensation judgment unit 34 judges whether the compensation is possible with respect to the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N by using Equation (2) in operation (S405). In this case, with respect to the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N that exceed the predetermined compensation range values, the compensation is not performed and the compensation process is terminated (N in operation (S405)).
  • the compensation rate calculation unit 35 extracts the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX in accordance with the respective colors of the output variation rates R ' x R x , G ' x G x , B ' x B x in operation (S406), and calculates the rate of the maximum values R ' MAX R MAX , G ' MAX G MAX , B ' MAX B MAX extracted using Equation (3) to the output variation rates R ' x R x , G ' x G x , B ' x B x as the compensation rates ( r x , g x , b x ) of the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N
  • the pulse width calculation unit 36 determines the pulse widths of the pulse signals for controlling the amount of current being supplied to the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N by converting the compensation rates ( r x ,g x ,b x ) into the pulse widths of the pulse signals in operation (S408).
  • Information on the determined pulse widths of the pulse signals is provided to the LED driver 20 in operation (S409), and the LED driver 20 controls the amount of current supplied to the corresponding color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N by providing the pulse signals corresponding to the provided pulse widths to the color LED groups 11, 12, and 13 of the LED block 10-1 to 10-N in operation (S410).
  • the pulse widths of the pulse signals provided to the color LED groups 11, 12, and 13 of the LED blocks 10-1 to 10-N of which the compensation is performed become narrow in comparison to the existing ones, and thus, the amount of current being supplied to the LED blocks becomes smaller than the existing one.
  • the degree of aging of the color LED groups of the LED blocks is judged using the output differences among the respective LED blocks, and a relative large amount of current is supplied to the aged LED group in comparison to other LED groups. Accordingly, the non-uniformity of colors among the LED blocks occurring due to the aging may be removed, and thus, the picture quality is improved with the user's satisfaction sought.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Circuit Arrangement For Electric Light Sources In General (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Led Devices (AREA)
EP07108327.3A 2006-09-26 2007-05-16 LED-based optical system and method of compensating for aging thereof Expired - Fee Related EP1906710B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
KR1020060093439A KR100787221B1 (ko) 2006-09-26 2006-09-26 Ｌｅｄ 기반 광시스템 및 그의 노화 보상방법

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EP1906710A3 EP1906710A3 (en) 2012-01-25
EP1906710B1 true EP1906710B1 (en) 2018-03-07

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CN105912293B (zh) * 2016-03-31 2019-02-22 Oppo广东移动通信有限公司 一种智能终端设备
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KR100787221B1 (ko) 2007-12-21
US7920111B2 (en) 2011-04-05
EP1906710A2 (en) 2008-04-02
EP1906710A3 (en) 2012-01-25
CN101154338B (zh) 2010-10-13
CN101154338A (zh) 2008-04-02
US20080077363A1 (en) 2008-03-27

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